1. Field of the Invention
The present invention relates to a magnetic pole position detecting device that detects a magnetic pole position of a rotor in a permanent-magnet synchronous motor.
2. Description of the Related Art
In a permanent-magnet synchronous motor (hereinafter, referred to simply as a motor) that includes a rotor including permanent magnets and that includes a stator including coils, electric currents are applied to the coils in accordance with a magnetic pole position of the rotor so that desired torque can be obtained. For this reason, while the magnetic pole position of the rotor is detected by a sensor such as an encoder, electric currents are applied at an appropriate exciting phase to drive and control the motor. Accordingly, in such a motor, at the time of starting the motor, position matching between a reference position of the sensor and the magnetic pole position of rotor is performed. A method of detecting a magnetic pole position of a rotor for such a purpose is disclosed in Japanese Patent No. 3408468, Japanese Patent No. 4816645, Japanese Patent No. 3805336, Japanese Laid-Open Patent Publication No. 2011-50198, and Japanese Patent No. 3971741, for example.
However, in a conventionally known method, accuracy of detection may be decreased due to a noise included in a feedback signal, friction acting on a rotor, external force caused by unbalance of a load, or the like. Further, in a method of detecting a magnetic pole position by moving a rotor, a movement amount of the rotor possibly becomes large, so that this method is not preferable from a standpoint of practical aspect. Furthermore, if coils of a motor are connected to amplifiers in a wrong connection order, if the number of magnetic poles of a motor is incorrectly set up, or if resolution of a sensor is incorrectly set up, or in a similar case, a magnetic pole position cannot be accurately detected.
An object of the present invention is, in a magnetic pole position detecting device that detects the pole position of a rotor, to prevent detection accuracy from decreasing due to a noise, friction, or external force, and to appropriately find false detection of a magnetic pole position so that safety and reliability of a motor can be improved.